Active vibration control of a sphere using rotary oscillations

Investigating the vortex-induced vibrations (VIV) of a sphere offers us not only the opportunity to better understand fundamentals of fluid-structure interaction, but also to develop practical control approaches of VIV. In this study, we impose high-frequency rotary oscillations on a sphere as a control method to disrupt large-scale vortex formation in the wake. The effects of rotary oscillation frequency and amplitude were first investigated to gain an understanding of vortex suppression mechanisms and to define the bounds of open-loop control effectiveness. It was found that the effects of high-frequency rotary oscillations varied across the range of vibration modes investigated. For the mode II branch, optimal tuning of the oscillation frequency resulted in an 84% reduction in VIV amplitude. Subsequently, an attempt was made to further suppress VIV by implementing a closed-loop control system.